Historically, rigid supports were used long before the adoption of flexible fabric supports. Most of the earliest icons still in tact from the 2nd and 3rd century are on wood panels. During the Renaissance a large portion of the paintings were also on solid wood panels. Italian painters were known to use poplar, while their Northern counterparts were using oak (later they would move on to mahogany). The wood was first dried well and sanded very smooth. It was then covered with a layer of liquid gesso made by mixing gypsum (a white chalk pounded into powder), with glue made from animal skins. Then, the wood panels were sanded and burnished until they were smooth, and ready for painting. The fact that we still have so many of these paintings with us today is proof that a properly primed and maintained panel withstands the test of time.
Traditionally solid wood panels were used in the Renaissance and continue to be used by some artists today. There is a great variety of solid wood panels, so it is important to choose one that is rigid, has a uniform grain, and has a low acidity. Avoid painting on softwoods or semi hardwoods such as pine or poplar. These woods are more porous, making them more susceptible to warping, and also have a higher acid content. Due to the potential for warping, a solid wood panel should be at least 1″ thick. It is also important to note how the panel is cut. A radially cut panel will have the grain running perpendicular to the face of the panel, and thus will be more stable than the more common tangentially cut panels, whose cut along the grain will tend to cause warping or twisting over time. In addition, solid panels cannot be braced (cradled) on their back. Due to the varying rates of expansion and contraction across a panel, a rigid bracing would actually cause the panel to buckle and bow in order to constrain to the bracing system.
While the original panel paintings were all made on solid wood panels, there are many more options available for artists today. Technology has created numerous types of manufactured panels, engineering them to have very specific attributes, and eliminating some of the original weaknesses in solid wood panels. A solid panel still has all the original cellular structure of the tree from which it was made. This structure is susceptible to expansion and contraction as the wood is exposed to different climatic and environmental changes. For example, over time wood can warp or split moving from wet to dry climates. Manufactured panels in contrast, break down the cellular structure of the wood, enabling a more uniform, stronger, and stable panel that can weigh less.
Unlike the masters of the past, the modern painter has numerous choices available when it comes to choosing a panel for painting. Four of the main factors to consider are a panel’s:
1. Density: The denser a panel, the less moisture it will absorb, making it less likely to warp. It is also easier to prime because the wood will not absorb the primer as quickly, reducing the amount of layers needed to seal and coat a panel.
2. Grain: If a wood has a heavy grain, it will require more layers of gesso to ensure that the grain does not come through the coating. Also, within the same type of wood there can be great variations in density along the lines of the grain. Woods can grow more or less dense with varying temperatures through the year, or even in ‘stressful times’ such as drought, and this varying density can cause warps or cracks along the lines of the grain.
3. Acidic Content: Considering the acidic content of the panel is important in order to avoid SID (Support Induced Discoloration – or yellowing). Softwoods or semi hardwoods, such as pine or poplar, generally have a higher acid content, and are more prone to causing SID through leaching. Hardwoods generally have a lower acidity, though we’ll see there are exceptions to this rule. It is best to do some research to determine what is the acidic content of the wood you are using before beginning to prime a panel.
4. Type of Engineered Wood: While engineered wood such as hardboard, plywood, and MDF can offer substantially better dimensional stability over solid wood panels for artists, it is important to understand the pros and cons of each of these surfaces and how different panels are braced. In upcoming blogs we will discuss these differences and the differences in the materials used to brace panels.
There is a lot more to come on this topic, so stay tuned for more in the series: Painting on Panel.
All things Ampersand,
Artist & Social Media Specialist
Ampersand Art Supply
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